The present invention relates to filter elements.
More particularly, the present invention concerns tubular filter elements for filtering liquids in a pressure filter apparatus.
It is known in the prior art (see German Offenlegungsschrift No. 2,741,639) to provide a tubular filter element for a pressure filter. Such a filter element is closed at its lower side and is open at its upper side which is fixed on a supporting member. The side walls of the filter element bound an interior which is filled with a loose filling material. The filling material includes a plurality of ball-shaped members of known material. The balls are so closed-packed that the outer surfaces of the filter element are supported by them in a substantially smooth configuration. Filtrate is directed into the filter element from outside and filtrant leaves the element from the inside of the same.
Such a filter element has a disadvantage, in that the filter cake which formes at the exterior of the filter element does not, during back flushing, drop everywhere and completely from all parts of the outer surface of this filter element. Only a partial removal of the filter cake takes place and this results in local drops in pressure along the outer surface, which fact prevents clean removal of the remaining parts of the filter cake from this surface.